At the present time, in view of 3D compatibility or reduction in load on peripheral devices/apparatuses, an increase in speed of liquid crystal has been an important development subject. Heretofore, although an increase in speed has been studied by improvement in physical properties of nematic liquid crystals and/or improvement of panels, development of a high-speed liquid crystal other than a nematic liquid crystal has also been actively carried out. As liquid crystals which are not nematic liquid crystals and which can perform high speed response, for example, a ferroelectric liquid crystal (FLC), a liquid crystal which exhibits an optically isotropic liquid crystal phase (optically isotropic phase), such as a blue phase (for example, see Non-Patent Literature 1), and a biaxial liquid crystal have been currently known.
A blue phase is classified into blue phases I and II, each of which is an ordered phase having a cubic structure, and a blue phase III which is an amorphous (disordered) phase. Since those blue phases each have optically isotropy when no electric field is applied, the rubbing alignment is not required; since clear black is obtained without any light leakage, the contrast is excellent; and in addition, since the electric field is horizontally applied as in the case of an IPS method, the viewing angle is also excellent. Furthermore, since switching is performed based on the exhibition of birefringence using a Kerr effect, high speed response can be obtained in principle.
In a liquid crystal optical element using a blue phase liquid crystal, a very narrow exhibition temperature range (approximately 1°) of a blue phase has been a problem (for example, see Non-Patent Literature 2). However, in recent years, it was found that the temperature range exhibiting a blue phase can be increased by polymerization. For example, Non-Patent Literatures 3 to 5 have reported that in a low molecular weight liquid crystal material exhibiting a blue phase, when a small amount of a polymerizable compound is polymerized to form a polymer while the blue phase is maintained, the blue-phase exhibition temperature range is increased to several tens of centigrade degrees (polymer-stabilized blue phase). In addition, Patent Literatures 1 and 2 have disclosed that when polymerization of a mixture containing a polymerizable compound and a liquid crystal material having chirality is started at a temperature at which the mixture exhibits an isotropic phase or a blue phase and is then finished in an optically isotropic state substantially without scattering of light having a wavelength equal to or more than that of visible light, a highly transparent and an isotropic liquid crystal-polymer composite material having a large and stable Kerr coefficient in a wide temperature range can be obtained. In addition, Patent Literatures 3 and 4 each have disclosed that as a liquid crystal material having chirality which is used to form a polymer-stabilized blue phase, a liquid crystal composition containing a compound having a CF2O group or a chlorobenzene ring in a mesogenic portion is preferable. Furthermore, Patent Literatures 5 to 7 each have disclosed that as a polymer used to form a polymer-stabilized blue phase, a polymer obtained from one reactive mesogenic polymerizable compound, a polymer formed by copolymerization between methacrylic skeletons and acrylate skeletons, or a polymer obtained from a polymerizable compound having an asymmetric structure is preferable. In addition, Patent Literature 8 has reported that by blending a soluble liquid crystal polymer having chirality with a liquid crystal composition, the exhibition temperature range of a blue phase of this liquid crystal composition is increased.
A blue phase which is generally used is a blue phase I or II, and a blue phase which is polymer-stabilized by the method described above is also a blue phase I or II. In contrast, the number of liquid crystals each exhibiting a blue phase III is very small, and the stabilization thereof is also difficult. Although the number of reports on exhibition of a blue phase III and stabilization thereof is small, for example, Non-Patent Literatures 6 and 7 have disclosed that when a T-type chiral liquid crystal oligomer having an intramolecular twisted order is blended with a nematic liquid crystal composition, a blue phase III can be exhibited, and that the exhibition temperature range thereof can also be increased. In addition, Non-Patent Literature 8 has proposed that the order of a blue phase is disturbed by a cybotactic layer structure, and a blue phase III is exhibited. Furthermore, Non-Patent Literature 9 has reported that as in the case of blue phases I and II, in the case of a blue phase III, when a polymer is formed in a nematic liquid crystal composition by polymerization of a small amount of a polymerizable compound, the exhibition temperature range of a blue phase III can be increased.